Bought a used iPhone 4 sprint how do I switch it?

Its one of the ones that doesn't have a sim card slot. I'm on sprint and its a sprint phone.

If you hold the button on the top right corner of the IPhone for a few seconds, then it
should switch on. If not, contact the original user of the phone and find out what's up
because that is how all IPhones turn on.

Go to sprint store to activate it as long as its not a lost or stolen phone itll work